The invention relates to a solar cell comprising a transparent base electrode preferably formed of doped stannic oxide and comprising a semiconductor body formed of amorphous silicon which contains an intrinsic (i) layer between a p-SiC layer and an n-doped layer, said (i) layer having a phosphorus doping.
J. Appl. Phys. 54 (11), pages 6705 through 6707 as well as Appl. Phys. Letters 44 (11), pages 1092 through 1094, both incorporated herein by reference, disclose solar cells which comprise a boron doping profile in the i-layer. A high efficiency of up to 9.45% and good fill factors of 0.72 are thus achieved. The cells are formed on glass substrates and the light is incident from the p-side.
German Patent Application P 24 39 088.5, corresponding to U.S. Ser. No. 739,702, filed May 31, 1985, incorporated herein by reference, proposes a solar cell wherein the light is incident from the n-side and which comprises a linearly decreasing boron doping profile in the direction of the i/n junction in order to improve the stability.
Thin film solar cells of amorphous silicon (a-Si) having the layer sequence p-SiC/i/n generally exhibit what is referred to as the Staebler-Wronski effect to a more or less pronounced degree. Upon illumination, particularly when the cell is operated in an open circuit condition, i.e. a no-load voltage is present, a reversible decrease of the efficiency (for example by about 18% for an illumination of 100 mW/cm.sup.2 having a time duration of 16 hours) can occur as a result of this effect. In this case, reversible means that the initial values of the efficiency can be achieved again after 30 minutes by tempering the cell at, for example, 180.degree. C. Although the decrease of the efficiency diminishes with time, such cells can only be employed for technical applications under certain conditions.
The Technical Digest of the International PVSECH-1, Kobe, Japan, pp. 217-220, incorporated herein by reference, discloses a solar cell of the type initially cited which achieves a reduced light aging by means of a phosphorus level of about 0.5 ppm which is constant over the i-layer. The improvement in stability thus achieved is, however, too low due to the low level of phosphorus concentration. Use of higher levels of phosphorus would lead to a great reduction in efficiency.